1. Field of the Invention
The present invention relates to a rail grinding unit for grinding surface irregularities on a rail head of at least one rail of a railroad track having two rails, which comprises a support frame having opposite ends, an undercarriage having flanged wheels supporting each support frame end on the rails for mobility along the railroad track, a vertically adjustable carrier frame mounted on the support frame, an endless grinding band mounted on the carrier frame and trained about guide rollers under tension for rotation thereabout, a lower one of the guide rollers constituting a pressure roll for pressing the endless grinding band into grinding contact with the surface, and drive means for moving the endless grinding band about the guide rollers.
2. Description of the Prior Art
U. S. Pat. No. 4,249,346, dated Feb. 10, 1981, discloses a continuously advancing rail grinding machine for grinding surface irregularities on a rail head of a railroad track rail The machine has a sequence of tool carriers with sliding whetstones as grinding tools. A crank drive reciprocates the tool carriers to impart an operating movement to the whetstones and the reciprocating operating movement is superimposed on the continuous forward movement of the machine to obtain a high grinding efficiency. The patent also discloses an embodiment of a rail grinding machine wherein the rail grinding tools are vertically adjustable endless grinding bands trained about two guide rollers arranged sequentially in the direction of the track. A drive motor continuously moves the grinding band about the guide rollers to impart an operating movement to the grinding band which is superimposed on the continuous forward movement of the machine. This produces a high grinding efficiency while producing high-quality grinding of the rail head surface.
Austrian Pat. No. 221,131, of Oct. 15, 1961, discloses a rail grinding machine comprising a grinding unit with a rail grinding band. The grinding unit is vertically adjustably linked to the frame of the machine and is supported on the track rails by flanged rollers. The rail grinding band is trained about two guide rollers facing the running surface of the rail head of a respective track rail and is then reeled over a drive crank. As soon as a section of the grinding band in operating contact with the rail head running surface is worn out, this grinding band section is reeled over the drive crank to expose a subsequent grinding band section reeled off a storage roll. The grinding movement of the grinding band is provided only by the forward movement of the machine and the grinding efficiency is, therefore, very low while the operating life of each grinding band section is very short because of the linear contact thereof with the rail head surface.
European Pat. No. 0 110 246, whose grant was published Feb. 19, 1986, discloses a rail grinding machine which is manually movable along one or both rails of a railroad track. The machine comprises a grinding unit with a frame supported by flanged rollers on the track and an endless grinding band trained over two guide rollers mounted thereon. A carrier frame connected to the grinding band and an actuating motor is manually vertically adjustable with respect to the grinding unit frame by means of a screw drive and is rotatable about a vertical axis. In addition, the carrier frame with the endless grinding band is manually pivotal with respect to the grinding unit frame about an axis extending in the longitudinal direction of the track to incline the grinding band to a desired extent with respect to the rail head. The machine may be removed from the track on an outrigger equipped with rollers. Such a light, manually operated machine has a low grinding efficiency and is used only for spot grinding, accurate surfacing being impossible because of the manual operation. Coupling this machine to a motor-driven car will not avoid these disadvantages but will even cause additional down times to permit intermittent manual adjustments. Furthermore, the profiled pressure roll constituted by one of the guide rollers extends far beyond the rounded edges of the rail head, which causes an excessive transverse curvature of the grinding band, leading to a short operating life of the band.